Thermally stable lubricants for external combustion engines

ABSTRACT

Alkylated aromatic hydrocarbons have been found to serve as lubricants, exhibiting excellent thermal stability, for Rankine Cycle Engines especially when using aqueous nitrogen-containing hydrocarbon motive fluids.

United States Patent [191 Clipper et al.

THERMALLY STABLE LUBRICANTS FOR EXTERNAL COMBUSTION ENGINES Inventors:Robert A. Cupper, Ridgefield,

Conn; George S. Somekh, New Rochelle, NY.

Union Carbide Corporation, New York, NY.

Filed: Apr. 13, 1973 Appl. No.: 350,800

Assignee:

References Cited UNITED STATES PATENTS 3/1965 Pappas et al 252/59 X [451Sept. 10, 1974 3,183,190 5/1965 Schick et al. 252/59 3,288,716 11/1966Becraft et a1. 252/59 3,511,049 5/1970 Norton et al. 60/36 3,538,17811/1970 Sias 252/59 X 3,584,457 6/1971 Davoud 60/36 PrimaryExaminer-Edgar W. Geoghegan Assistant Examiner-H. Burks, Sr. Attorney,Agent, or Firm-Bernard Francis Crowe 5 7] ABSTRACT Alkylated aromatichydrocarbons have been found to serve as lubricants, exhibitingexcellent thermal stability, for Rankine Cycle Engines especially whenusing aqueous nitrogen-containing hydrocarbon motive fluids.

8 Claims, .No Drawings BACKGROUND OF THE INVENTION This inventionpertains to the use of alkylated aromatic lubricants in externallyheated engine systems using aqueous nitrogen-containing motive fluidsfor converting heat energy to mechanical energy and in particular totheir use in automotive Rankine Cycle engine systems.

In a simple Rankine Cycle system there is a liquid pump for pumping themotive fluids to the required boiler pressure, a boiler for heating andevaporating the motive fluid, an expander for converting heat energy inthe motive fluid into mechanical energy and a condenser for liquifyingthe motive fluid vapors exhausted from the expander.

The liquid pump can be any one of a variety of types, such as a gear ora piston-type pump. In such pumps the lubricant is usually brought intocontact with the motive fluid. In order to operatesatisfactorily in sucha pump the lubricant must have a low pour point and low temperatureviscosities that are not excessive, that is, less than about 10,000centistokes at F. The lubricant should also have low solubility in themotive fluid at low temperatures, i.e., 0 to 180F., in order to minimizepump wear and to minimize the amountof lubricant passing into theboiler. The lubricant and motive fluid should be nonemulsifying for thesame reason. Additionally, the lubricant should have a minimum effect onthe wear of the pump parts.

Since it is inevitable that some of the lubricant will enter the boilerwhether it comes through the liquid pump or from an external source, itis essential that the lubricant be stable at the high temperaturesencountered in the boiler. These boiler temperatures are at least 550F.(288C) The operating temperatures in the expander regardless of the typeused are almost as high as the maximum boiler temperatures. In areciprocating pistontype expander the lubricant used to lubricate thepistons comes in contact with the motive fluids and should therefore becompatible with them. In certain turbine expanders some motive fluid isused to lubricate the bearings but this is generally unsatisfactorybecause of the low viscosity of the motive fluid and the fact that whenthe system is shut down the expander can go under vacuum resulting inair leaking into the system which can be very deleterious. It ispreferred therefore, to employ a lubricant for both improved lubricationand sealing.

In the condenser, the motive fluid exhaust vapors are liquified andcooled by heat transfer. If this motive fluid contains some lubricantbecause of contact hrough the expander, the lubricant can coat thecondenser surface leading to two possible serious problems. The coatingcan drastically reduce the capacity of the condenser to remove heat. Thesecond potential problem is that the lubricant can build up in thecondenser, thereby depleting the rest of the engine system of thislubricant supply or making such supply uncertain. It is, therefore,desirable that the lubricant be at least somewhat soluble in the liquidmotive fluid at the condenser temperature so that the lubricant isremoved from the condenser. Alternatively, it is desirable for thelubricant to be suspended but not emulsified in the liquid motive fluid.

The class of lubricants most widely used in existing Rankine Cyclesystems are solvent extracted and dewaxed lubricating oil fractions ofpetroleum. These refined mineral oils are generally not stable attemperatures over 500F. c260C.). Thus, in certain Rankine Cycle systems,they decompose to form gaseous products and even polymeric sludges orcarbon. The gaseous products reduce the capability of the condenser toliquify the motive fluid. The polymer sludge or carbon can coat theentire system, reducing heat transfer coefficients in both boiler andcondenser. The decomposition products increase the liquid entrainment ofthe lubricant in the motive fluid leaving the condenser and the liquidpump. These impurities can also increase the vapor entrainment, even tothe point of foaming, of the lubricant in motive fluid vapors exhaustingfrom the expander. Therefore, after a certain period of operation withthese refined oils, the system can become inoperative.

A closely related class of lubricants that has also'been used are thesuper-refined mineral oils. These are mineral oils that are highlysolvent extracted (to remove impurities as well as aromatic and somenaphthenic components), deeply dewaxed to obtain low pour points, andthen hydrogenated to eliminate unsaturated constitutents and certainsulfur-containing compounds. These super-refined mineral oils,therefore, consist almost entirely of paraffinic and naphthenichydrocarbons. Such oils are thermally stable up to about 550F. (288C).However, they are extremely expensive because the super-refiningprocedures, in addition to being costly, result in very low yields ofthis oil. Being highly aliphatic this type of lubricant has a very lowsolubility in most water-based motive fluids at condenser temperatures.Consequently, the only mechanism by which this type of lubricant can beremoved from the condenser surface is by entrainment.

Fluorinated hydrocarbons having high thermal stability have been used aslubricants but they are extremely expensive and very insoluble inaqueous motive fluids at condenser temperatures.

Many known lubricants cannot be used in Rankine Cycle engines because oftheir incompatibility with the motive fluid, thermal instability,reactivity with the motive fluid or poor physical properties. Forexample oxygenated silicone lubricants are decomposed by aqueousnitrogencontaining systems. Polyoxyalkylene glycol monoalkyl ethers lubricantsare thermally unstable under the temperature conditions encountered.Chlorinated polyphenyls have pour points which are too high for use inRankine Cycle systems as are those of polyaromatic polyethers, such aspolyphenylene oxides. Phosphorous derivatives prepared fromphosphonitrilic chlorides are susceptible to hydrolysis. The alkylesters such as diethylhexyl sebacate are also susceptible to hydrolysis.

All of the problems enumerated above are further compounded when anaqueous nitrogen-containing hydrocarbon motive fluid is used in place ofwater because of its solvent effect on the lubricant which tends toremove or dilute the lubricant and entrain it.

- SUMMARY OF THE INVENTION In the method of converting heat energy intomechanical energy which comprises heating a motive fluid to the vaporstate and utilizing the energy of the vaporized motive fluid to performwork in a Rankine Cycle system comprising a liquid pump, a boiler, anexpander, and condenser, an improvement has now been found whichcomprises lubricating said liquid pump and expander with a lubricantselected from the group consisting of at least one alkyl substitutedaromatic hydrocarbon or a mixture of at least one alkyl substitutedaromatic hydrocarbon and a diaryl alkane, said lubricant having arefractive index at 20C. of 1.490 to 1.575 and a density at 25C. of 0.86to 1.00 grams per milliliter wherein said aromatic hydrocarbons areselected from the group consisting of naphthalene, tetralin, anthraceneand phenanthrene and both the alkyl group and the alkane moiety of thediaryl alkanes contains about one to about 18 carbon atoms.

The lubricants of this invention can be produced by the alkylation ofthe respective aromatic hydrocarbons with individual olefins,chloroparaffins, alcohols, or mixtures of these reactants. Althoughnormal alpha olefins are'the preferred alkylating agents, commercialolefin mixtures containing branched chain olefins in minor proportionscan be tolerated.

Exemplary alkyl-substituted aromatic hydrocarbons include naphthalenesubstitution. products, such as, ln-pentadecyl naphthalene,l-n-hexyl-Z-cyclohexyl naphthalene, 1-methyl-2,7-di-tert-butylnaphthalene, l -methy-2,3,6,7-tetraisobutyl naphthalene, l-methyl-5-isopropyl-3,4,6,7,8-penta-tert-butyl naphthalene, and the like;anthracenes, such as l-octyl-4-tetra-de'cylanthracene,l-butyl-2-dodecyl-anthracene, 1,2-di-nbutyl anthracene,l-methyl-4-n-dodecyl-7-n-hexyl anthracene, l,2-diethyl-3,4,7,8-tetra-isobutyl-5-n-amyl- 6-n-hexylanthracene, and the like;phenanthrenes, such as, l-propyl-Z-dodecyl .phenanthrene, l-ethyl-4-tetradecyl phenanthrene, 1,3,5-tri-n-heptyl phenanthrene,l-methy-2,G-di-isobutyl-8-tetradecyl phenanthrene, and the like. Thediarylalkanes include: phenyl naphthyl alkanes, such as,1,4-di-tert-butyl-2- [n-butyl- (1,4-di-tert-butyl naphthyl)]benzene andl-toluyl-4-noctyl naphthalene, di-naphthyl alkanes, such as,l-n-decyl-S-[l-methyl naphthyl]naphthalene, andlmethyl-2-cyclohexyl-5-ethyl-7-[methyl-( l,5,6 ,7,8- penta-tert-butylnaphthyl]naphthalene; phenyl anthracyl alkanes, such as,l-isobutyl-2-methyl-5-]l0-nbutyl( l,2,4,6-tetraisobutyl-6-methylanthracyl]benzene; naphthyl anthracyl alkanes, such as, l- [3-h-ocytl-6-tert-bu tyl;6-( 2-tert-butyl napthy1)]anthracene and1,6,8,9,10-penta-tert-butyl-2-[ethyl-( 1,8- di-tert-butylnaphtyl)]anthracene; di-anthracyl alkanes, such as, bis-( 1,8'-anthracyl)- l l S-n-Octadecane andl-ethyl-2,3-di-n-butyl-9-methyl-5-[ l-n-butyl-3,(lethyl-Z-cyclo-pentyll-isobutyl anthracyl )-9-(n-butyl- 1)]anthracene;phenyl phenanthyl alkanes, such as lmethyl-6-[ 2n-hexyl-6 l -tert-butylphenyl- 2]phenanthrene and 6,8-dimethyll,2,3,9-tetra-nbutyl- 10-isopropyl-7[ l-n-propyl-3 )-2-( l ,5,6-triethyl phenyl) lphenanthrene;naphthyl phenanthryl alkanes, such as,1,3-di-methyl-2-[n-undecyl-2-naphthyl-9]-3- methyl phenanthrene andl,4,5,7-tetra-tert-butyl-8- methyl-2-( 1-n-butyl-4)-( 7l-tert-butyl,4-9-diethyl, l0- methyl phenanthryl1naphthalene; anthracylphenanthryl alkanes, such as, 3-tert-butyl-l-(l-n-butyl-4)-2-(3-methyl-l-tri-decyl anthracyl) phenanthrene; diphenanthryl alkanes,such as, 7,lO-dimethyl-9-ethyll ,8-di-n-butyl-2-[ methyl-2 l0-methyl-9ethyll -nbutyl phenanthryl]phenanthrene; phenyl alkyltetralins, such as, 7-](l-n-octyl-5)-phenyl]tetralin, and 3- ethyll,7-di-n-butyl-- l-n-.butyl-4)- l -dimethyl phenyl-4)]tetralin; naphthylalkyl tetralins, such as, 1- methyl-4,5,8,9-tetra-n-buty1-2-[ 7-methyl l-isopropyl-3-isobutyl tetralyljnaphthalene, and S-methyl-l 7-noctylnaphthyl-l ltetralin; anthracyl alkyl tetralins, such as,Z-propyl-3-ethyl-7-n-butyl-5-[ l'-n-butyl-4)-8- methyl-5,7,IO-tri-isobutyl anthracyl-2]tetralin and lmethyl-8-[(l-n-butyl-2)-6-tert-butyl anthracyl ltetralin; phenanthryl alkyltetralins, such as, 3-[( l-tetradecyl- 14)-tetralyl-5]phenanthrene and2,3,8-tri-tert-butyll0-{5-( l-n-buty|-4)-l ,7-di-tert-butyl tetralylphenanthrene; and alkyl di-tetralins, such as, 3,5-nbutyl-7-[2-(l-ethyl-2)- l -ethyl-7,8-di-n-butyl tetralyl 1- tetralin and 5-[5-(l-n-octyl-8)-7-methyl tetralyljtetralin; diphenyl alkanes, such as,1,4-dimethyl-2-[n-butyl phenyllbenzene, l-methyl-Z-[n-heptylphenyl]benzene, and l,3-diethyl-5-[methyl-(4,5-diisopropyl-3- methylphenyl]benz'ene.

The lubricants of this invention must strike a balance between aromaticand aliphatic properties to meet the peculiar requirements of RankineCycle Engines using aqueous nitrogen-containing hydrocarbon motivefluids. One measure of this balance has been found to the refractiveindex of the lubricant.

Although the refractive index range at 20C. can extend from 1.490 to1.575, it is preferred to use lubricants having a refractive index inthe range of 1.500 to 1.575.

Another measure of the balance between aromatic and aliphatic propertiesof the lubricant is density.

Although the density of the lubricants of this invention can range from0.86 to 1.0 grams per milliliter, it is preferred to use those having adensity in the range of 0.88 to 0.96.

Below the lower limits of refractive index and density, given above,alkyl substituted aromatic hydrocarbons are less stable thermally andhave insufficient solubilities in aqueous nitrogen-containinghydrocarbon motive fluids. Above the upper limits of refractive indexand density prescribed above, alkyl substituted aromatic hydrocarbonshave excessively high pour points and the viscosity-temperaturecharacteristics, such as, viscosity index are unsatisfactory.

Another requirement for lubricants in Rankine Cycle Systems is that thebe somewhat soluble in the motive fluid to the extent of about 0. 1 to7.5 percent by weight at 185F. This provides a means for removing fromthe condenser walls any lubricant which mechanically is entrained in themotive fluid vapors and deposited thereon. Deposits of lubricant on thecondenser walls are undesirable because they are poor heat conductorsand hence upset critical heat transfer functions. This relationshipbetween motive fluid and lubricant is unexpected because the former isaqueous and the latter non-aqueous which normally would preclude such acombination.

The choice of motive fluid used in this invention is not narrowlycritical and includes water; aqueous nitrogen containing hydrocarbonscontaining from about 25 to about percent by weight of anitrogen-containing hydrocarbon selected from the group consisting ofpyridine, 2-methy1 pyridine, 3-methyl pyridine, 4-methyl pyridine,2,6-di methyl pyridine, 1,2-diazine, 1,3- diazine, and 1,4-diazine;phosphorous halides, such as, phosphorous trichloride, phosphoroustribromide, phosphorous bromodichloride, and the like; titanium halides,such as, titanium tetrachloride, titanium tetrabromide, titaniumtetrafluoride, dichloro-dibromo titanium, and the like; silicon halides,such as, silicon tetrachloride, trichlorosilane, dibromochlorosilane,iodotrichlorosilane, silicon tetrabromide, dichloroiodo-silane, and thelike; fluorinated cyclic amines; tetraalkylsilanes, such as,tetramethylsilane, tetraethylsilane, tetrapropylsilane,tetraisopropylsilane, and the like; alkyl halosilanes, such as,methyltrichlorosilane, trimethylchlorosilane, trimethylfluorosilane,ethyltrichlorosilane, diethyldifluorosilane, methyldichlorosilane,trichloromethylsilane, and the like; and fluorinated alcohols, such as,trifluoroethanol, trifluoropropanol, and the like.

The preferred motive fluids are the aqueous-nitrogen containingcompounds enumerated above.

Although not essential, minor amounts of additives can be incorporatedin the lubricants used in this invention as for example antioxidantssuch as zinc dialkyl or diaryl dithiophosphates, aromatic amines, alkylphenols and the like; corrosion inhibitors such as alkaline earthalkaryl sulfonates, heterocyclic nitrogencontaining compounds as forexample benzimidazole or benzotriazole; dispersants such as imide/amidesderived from long chain alkenyl succinic acids or anhydridesinterreacted with various amino compounds, such as ethylenediamine,diethylenetriazine, triethylenetetraamine, tetraethylenepentamine,piperazine and alkyl or hydroxy-alkyl substituted alkyleneamines orpiperazines, or polyols such as trimethylol propane or pentaerythritol;or viscosity index improvers such as polyacrylates, polymethacrylates,polyolefins and the like.

The invention is further described in the examples which follow. Allparts and percentages are by weight unless otherwise specified.

The lubricants in this invention as well as structurally relatedarylalkanes which do not function as satisfactory lubricants (Controlexperiments) are described below.

LUBRICANT A Lubricant A used in Control A is a commercial grade of highquality mid-continent, solvent extracted mineral oil having a viscosityof 200-210 SUS (Seconds Universal Saybolt) and 44.0 centistokes at100F., a viscosity index (ASTM D-567) of 95 minimum, a refractive indexof 1.4762 at 20C., and a density of 0.865 grams per ml. at 25C.

LUBRICANT B LUBRICANT C Lubricant C used in Control C was synthesized byalkylating 0.6 to one moles of a product (obtained by the Fridel-Craftsalkylation of benzene with chlorinated C to C n-alkanes) with n-decenefor about 1.5 hours at 105 to 107C. in the presence of 0.05 moles ofaluminum chloride catalyst. Lubricant C contains about 30 to percent byweight of alkyl tetralins, l to 10 weight of alkyl naphthalenes and 10to 30 percent alkyl benzenes. Up to about 20 weight percent dialkylbenzenes, where the alkyl groups have 11 to 15 carbon atoms, can beadded to improve viscosity index and pour point properties. Lubricant Chas a refractive index of 1.4492 at 20C., a density of 0.8862 g./ml. at25C. a viscosity of 9.63 centistokes at 100F. (l8C.).

LUBRICANT D Lubricant D used in Example 1, was synthesized by alkylatingone mole of a mixture of: (a) about 20 percent by weight of Lubricant C,(bB) about 65 percent by weight of dialkyl-benzenes wherein the alkylgroups contain about 1 l to 15 carbon atoms, (c) about 5 to 10 percentby weight of diphenyl alkanes wherein the alkane contains about 11 to 15carbon atoms and (d) about 5 to 10 percent by weight of a mixture ofanthracene and phenanthrene with about 0.6 moles of n-tetradecene-l forabout 1.5 hours at a temperature of about 105 to 107C. using an aluminumchloride Friedel- Crafts catalyst. Lubricant D has a refractive index of1.4902 at 20C., a density of 0.864 g./ml. at 25C., a viscosity of 2.218,55.3 and 7.8 centistokes at 0F. (--l8C.), 100F. (38C.) and 210F. (98C.)respectively and an aniline point of 165F. (74C.).

Lubricant D has a solubility of 0.1 percent in a 75:25 weight mixture ofpyridinezwater at 185F. (C.) and in a 60:40 weight mixture ofpyridinezwater at about 200 to225F. (93 to 108C).

LUBRICANT E Lubricant E used in Example 2 was synthesized in the samemanner as was Lubricant D with the exception that about 1.3 moles ofn-tetradecenel were used. Lubricant E has a refractive index of 1.4926at 20C., a density of 0.870 g./ml. at 25C., a viscosity of 1.587, 40.4and 6.1 centistokes at 0F. (l8C.), F. (38C.), and 210F. (98C.)respectively and an aniline point of about 194F. (90C.).

Lubricant E has a solubility of 0.2 percent in a 75:25 weight mixture ofpyridine:water at 185F. (85C.).

LUBRICANT F EXAMPLE 1 A stainless steel autoclave having a void of 300ml. was charged with 25 ml. of Lubricant D together with ml. of the60:40 weight per cent mixture of pyridinezwater. The autoclave waspurged with nitrogen, closed and agitated at 572F. (300C) for 168 hours.When the autoclave was opened it was found that little change had takenplace in either the lubricant or the aqueous pyridine. This stability atelevated temperatures plus the limited solubility in the pyridinezwatermixture indicated that Lubricant D would serve well in a Rankine Cyclecondenser and liquid pump using pyridine:water as the motive fluid.

EXAMPLE 2 Example 1 was repeated with the exception that Lubricant E wassubstituted for Lubricant D and the autoclave experiment was performedat 662F. (350C. for

168 hours. Both the lubricant and the 60 percent pyridine: 40 percentwater mixture were left unchanged in appearance and there was noresidual pressure. These observations indicate that Lubricant E can besuccessfully used with pyridinezwater motive fluids under the conditionsfound in a Rankine Cycle system.

EXAMPLE 3 Example 2 was repeated with the exception that Lubricant F wassubstituted for Lubricant E.

The autoclave experiment at 662F. (350C) for 168 hours with Lubricant Findicated that both the lubricant and the pyridine:water mixture weresubstantially unchanged in both physical properties and appearance, andthere was no residual pressure. These observations indicate thatLubricant F can be successfully used with pyridinezwater mixture motivefluids under the conditions found in a Rankine Cycle system.

EXAMPLE 4 Example 3 was repeated with the exception that the autoclavewas held at 707F. (375C.) for 168 hours. Little change took place in theproperties of the lubricant. The only noticeable change was a drop ofonly 9 percent in the initial viscosity.

EXAMPLE less than 0.1 percent at 185F. (85C.) This limited solubility isunsuitable for this lubricant to be dissolved off the surfaces of aRankine Cycle System condenser.

When the autoclave was opened after 168 hours at 662F. (350C. it wasfound that the lubricant tended to fizz and foam. in view of these testresults Lubricant A was judged unacceptable as a lubricant for RankineCycle System using aqueous pyridine motive fluids. CONTROL B Example 2was repeated with the exception that Lubricant E was replaced byLubricant B. The solubility at 185F. (85C.) in a 75:25 weight per centpyridine:- water mixture was found to be less than 0.1 per cent. it wasobserved that the autoclave pressure unlike Example I increasedfrom'2,700 psig to 3,600 psig during the 168 hours of heating at 662.20F. (350C). After opening the cooled system the lubricants fizzed andfoamed. The lubricant had become black with carbonaceous material. Fromthese observations it was concluded that Lubricant B was unacceptable asa lubricant in a Rankine Cycle System using aqueous pyridine as a motivefluid. CONTROL C Example 2 was repeated with the exception thatLubricant E was replaced by Lubricant C. As in the other controls thesolubility in the :25 weight per cent pyridinetwater at 185F. (C.) wasfound to be less than 0.l per cent. After opening the autoclavefollowing the 168 hours at 662F. (350C), the lubricant was found to bedark and to contain carbonaceous matter and foamed when shaken. Thislubricant was therefore found unacceptable as a lubricantin a RankineCycle System employing aqueous pyridine as the motive fluid.

Although the invention has been described in its preferred form with acertain amount of particularity, it is understood that the presentdisclosure has been made only by way of Example and that numerouschanges can be made without departing from the spirit and scope of theinvention.

What is claimed is:

1. in the method of converting heat energy into mechanical energy whichcomprises heating a motive fluid to the vapor state, and utilizing theenergy of the vaporized motive fluid to perform work in a Rankine CycleSystem comprising a liquid pump, a boiler, an expander, and condenser,the improvement which comprises using an aqueous nitrogen-containinghydrocarbon as the motive fluid and lubricating said liquid pump andexpander with a lubricant selected from the group consisting of at leastone alkyl substituted aromatic hydro carbon or a mixture of at least onealkyl substituted aromatic hydrocarbon and an alkylated diaryl alkane,said lubricant having an index of refraction at 20C. of 1.490 to 1.575and a density of from 0.86 to 1.00 grams per milliliter at 25C. whereinsaid aromatic hydrocarbon is selected from the group consisting ofnaphthalene, tetralin, anthracene and phenanthrene and both the alkylgroups and the alkane radical of the diary] alkanes contains about oneto about 18 carbon atoms.

2. Method claimed in claim 1 wherein the aromatic hydrocarbon isnaphthalene.

3. Method claimed in claim I wherein the aromatic hydrocarbon isanthracene.

4. Method claimed in claim 1 wherein the aromatic hydrocarbon isphenanthrene.

5. Method claimed in claim 1 wherein the alkylated aromatic hydrocarbonhas a refractive index of about 1.500 to 1.575 at 20C.

6. Method claimed in claim I wherein the alkylated aromatic hydrocarbonhas a density of about 0.88 to 0.96 at 25C.

7. Method claimed in claim 1 wherein the lubricant is the reactionproduct obtained by alkylating naphthalene with isobutylene underFriedel-Crafts conditions having an index of refraction at 20C. of about1.562, a density at 25C. of about 0.944 g./ml., a viscosity at 100F.(18C.) of about 50.0 centistokes and a viscosity at 210F. (98C.) ofabout 4.2 centistokes.

8. Method claimed in claim 1 wherein the aqueous nitrogen-containinghydrocarbon is aqueous pyridine containing from about 25 to aboutpercent by weight of pyridine.

9 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.34,166 Dated Sept. 10, 1974 Inventofls) R.A. Gunner and 6.8. Somekh Itis certified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

=-- Column 5, line +6, "'naphtyl" should read naphthyl Column 3, line46, [3' h-ocytl6tertbutyl;6' etc." should read [3 -noctyl-6-tertbutyl,6'-etc.-

Column 3, line 48, "naphtyl" should read naphthyl--.

Column 4, line 44, "Systems is that the be somewhat soluble etc."

should read-Systems is that they be somewhat soluble etc.

Column 5, line 54, l/n-decene-l/n-decenew-l/ri-tetradecene-l etc."

should read 'l/n-decene-l/n-tetradecene-l etc.

Column 6, line 26, "2.218" should read --2,2l8--.

Column 6, line 39, 1.587" should read -l,578- Column 6, line (-l8C.should read --'(38C.)--. Claim 7, line 6, "(-l8C.)" should read (3 8C.)--

Signed and sealed this 10th day of December 1974.

(SEAL) Attest:

MCCOY M. GIBSON JR. c. MARSHALL DANN Attesting Officer Commissioner ofPatents

2. Method claimed in claim 1 wherein the aromatic hydrocarbon isnaphthalene.
 3. Method claimed in claim 1 wherein the aromatichydrocarbon is anthracene.
 4. Method claimed in claim 1 wherein thearomatic hydrocarbon is phenanthrene.
 5. Method claimed in claim 1wherein the alkylated aromatic hydrocarbon has a refractive index ofabout 1.500 to 1.575 at 20*C.
 6. Method claimed in claim 1 wherein thealkylated aromatic hydrocarbon has a density of about 0.88 to 0.96 at25*C.
 7. Method claimed in claim 1 wherein the lubricant is the reactionproduct obtained by alkylating naphthalene with isobutylene underFriedel-Crafts conditions having an index of refraction at 20*C. ofabout 1.562, a density at 25*C. of about 0.944 g./ml., a viscosity at100*F. (-18*C.) of about 50.0 centistokes and a viscosity at 210*F.(98*C.) of about 4.2 centistokes.
 8. Method claimed in claim 1 whereinthe aqueous nitrogen-containing hydrocarbon is aqueous pyridinecontaining from about 25 to about 90 percent by weight of pyridine.